5.21. Set Up:
Take
to be upward. After he leaves the ground the person travels upward 60 cm and his
acceleration is
downward. His weight is
W
so his mass is
Solve: (a)
(at the maximum height),
gives
(b)
The freebody diagram for the person while he is pushing up against the ground is given in Figure 5.21.
Figure 5.21
(c)
For the jump,
(from part (a)),
gives
gives
Reflect:
To accelerate the person upward during the jump, the upward force from the ground must exceed the down
ward pull of gravity. The ground pushes up on him because he pushes down on the ground.
5.22. Set Up:
Let the acceleration be in the
direction.
Solve: (a)
Apply
to the four cars taken as a single object. The freebody diagram for this object is given
in Figure 5.22a.
m
is the mass of one car and
is the force that the engine exerts on the first car.
Figure 5.22
gives
and
(b)
Apply
to the last three cars taken as a single object. The freebody diagram for this object is given
in Figure 5.22b.
is the force that the first car exerts on the second car.
gives
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This note was uploaded on 03/06/2009 for the course PHYS 114 taught by Professor Shoberg during the Spring '07 term at Pittsburg State Uiversity.
 Spring '07
 Shoberg
 Acceleration, Mass

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